Ni-free Ti-based Shape Memory Alloys

Hee Young Kim, Shuichi Miyazaki

• Publisher: Butterworth-Heinemann
• Year: 2018
• Print ISBN:
  9780128094013
• eBook ISBN:
  9780128093849
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Ni-free Ti-based Shape Memory Alloys reviews the fundamental issues of biomedical beta-type Ti base shape memory and superelastic alloys, including martensitic transformation, shape memory and superelastic properties, alloy development, thermomechanical treatment and microstructure control, and biocompatibility. Some unique properties, such as large nonlinear elastic behavior and low Young's modulus, observed in metastable Ti alloys are discussed on the basis of phase stability. As it is expected that superelastic Ti alloys will further expand the applications of shape memory alloys within the biomedical field, this book provides a comprehensive review of these new findings in Ti-base shape memory and superelastic alloys. - Includes coverage of phase transformations in titanium alloys - Discusses mechanical properties and alloy development - Presents a review of Ti-based shape alloys and their applications

Chapter 1

Martensitic Transformation Characteristics

Abstract

Metastable Ti alloys exhibit a martensitic transformation from β phase to hexagonal martensite (α′) or orthorhombic martensite (α″) depending on the content of alloying elements. The characteristic of martensitic transformation strongly affects shape memory and superelastic properties. In this chapter, the martensitic transformation characteristics of Ti-based alloys are overviewed. The effects of alloying elements on transformation temperature, crystal structure and morphology of α″ martensite, and transformation strain are particularly reviewed. The effect of ω phase on the martensitic transformation behavior is also described.

Keywords

Transformation temperature; Transformation strain; Lattice corresponding; Habit plane; Self-accommodation; Interface; α″ Martensite; Crystal structure; Lattice strain; Omega phase

Contents

• 1.1 Introduction
• 1.2 Crystal Structure and Martensitic Transformation Temperature
  • 1.2.1 Crystal Structure of Parent and Martensite Phases
  • 1.2.2 Transformation Temperature
• 1.3 Crystallography of Martensitic Transformation
  • 1.3.1 Lattice Correspondence
  • 1.3.2 Transformation Strain
• 1.4. Morphology of Martensite Phase
  • 1.4.1 Habit Plane and Interface
  • 1.4.2 Self-Accommodation
  • 1.4.3 Antiphase Boundary-Like Stacking Fault
• 1.5 Omega Phase Transformation
  • 1.5.1 Crystal Structure and Lattice Correspondence
  • 1.5.2 Influence on Martensitic Transformation
  • 1.5.3 Influence on Shape Memory Properties
  • 1.5.4 Room Temperature Aging
• 1.6 Summary
• References

1.1 Introduction

Understanding of martensitic transformation is essential to develop shape memory alloys and to improve their properties since the shape memory effect is based on the reversible thermoelastic martensitic transformation. Martensitic transformation characteristics of β-type Ti-based alloys such as transformation temperature and habit plane have been investigated since the 1950s [1–6]. Duwez [1] first investigated the Mo content dependence of the martensitic transformation in Ti-Mo binary alloys using the thermal-arrest technique and reported that the martensitic transformation temperature decreases progressively with increasing Mo content. Liu and Margolin [2] investigated the composition dependence of martensite structure and habit plane in Ti-Mn alloys. In the early 1960s, Kaneko and Huang [7] systematically investigated the martensitic transformation temperature as a function of alloy composition in several binary titanium alloy systems, e.g., Ti-Nb, Ti-V, Ti-Mo, Ti-Al, and Ti-Sn. Since then, there have been continued efforts to understand the nature of martensitic transformation in Ti alloys. As a result, many aspec...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Chapter 1: Martensitic Transformation Characteristics
• Chapter 2: Shape Memory Effect and Superelasticity
• Chapter 3: Effect of Interstitial Alloying Elements on Shape Memory and Superelastic Properties
• Chapter 4: Thermomechanical Treatment and Microstructure Control
• Chapter 5: Unique Properties of Metastable Beta Ti Alloys Related to Martensitic Transformation
• Chapter 6: Biocompatibility of Superelastic Beta Ti Alloys
• Chapter 7: Fabrication and Characterization of Shape Memory Alloys
• Index